In order to protect against failures in a computer network, network devices, such as routers, may establish protection circuits or “backup tunnels” over paths that offer an alternative to a protected network element (e.g., link or node). The economics of backup bandwidth coupled with the ability to more easily perform computational analysis of backup paths has renewed interest in shared mesh protection, with shared risk link group (SRLG) diversity as one of the primary focuses.
With most low to medium speed (=<1 G) and some 10 G long haul transport services moving to packet, shared mesh protection becomes of interest in this domain as well. Shared Mesh Protection has traditionally been dealt with by allocating shared resources ahead of time, but not making the actual data plane connections (though some current techniques utilize partial path setup) until the failure occurs. The two issues that have caused the evolution in this direction are that traditional (non-packet) transport services only allow one circuit to be active on a given set of facilities (e.g. channel, sub-channels, lightwaves, x-connects) at a time, and that SRLGs are not perfect: simultaneous or very near simultaneous failures can occur.
Packet transport, (e.g., multiprotocol label switching, “MPLS”) allows multiple circuits (i.e., label bindings in MPLS) to be simultaneously setup. Current recovery mechanisms, however, impact circuits which otherwise would not be affected by a failure event, when an unanticipated or improperly-planned-for failure event occurs, leading to over-utilization of some facilities.